Unix

Unix is the robust, multi-user, multitasking operating system developed at Bell Labs that established the foundational design for modern computing systems.

Developed by Ken Thompson and Dennis Ritchie at AT&T Bell Labs starting in 1969, Unix fundamentally changed operating system design. Its core features—multi-user support, preemptive multitasking, and a hierarchical file system—provided a stable, secure environment. The critical decision to rewrite most of the system in the C language by 1973 ensured its portability, allowing it to run on diverse hardware platforms (PDP-7, PDP-11, VAX) and fostering its rapid adoption in academic and commercial sectors. This architecture and philosophy directly influenced countless descendants, including the entire BSD family, Linux, and Apple's macOS.

https://www.opengroup.org/unix